1. Field of the Invention
The present invention relates to a laser radiation apparatus which can be miniaturized.
2. Description of the Related Art
The use of lasers has broadened quickly in material processing, medicine and measurement areas in recent years. The kinds of these lasers include solid state lasers, gas lasers, fiber lasers and free electron lasers. In addition, laser light oscillation modes include continuous-wave (CW) mode and pulse mode, and any pulse duration and wavelength can be set.
Amongst these lasers, solid state lasers will be described. A solid state laser is an apparatus for producing laser light by radiating excitation light over a solid laser rod provided inside the laser radiation apparatus. The oscillation of laser light using ruby by Maiman marked the beginning of the history of solid state lasers. Moreover, it is well known that a solid state laser in which YAG is the body material of a laser rod, named from the initials of yttrium, aluminum and garnet (see, for example, patent document 1).
FIG. 1 shows a simplified configuration of a conventional solid state laser radiation apparatus. Solid state laser radiation apparatus 1 basically includes a laser rod 2, which oscillates laser light, reflection mirror 3 and reflection mirror 4 for amplifying oscillated laser light, flashlamp 5 for emitting light energy over laser rod 2, power supply 8 for making flashlamp 5 emit light, and lens barrel 6, which covers the whole of flashlamp 5 and reflects and radiates light to laser rod 2.
Instead of reflection mirror 3 and reflection mirror 4, there are cases where a reflection coating is formed at either end face of laser rod 2. Reflection coating (for example, dielectric multilayer coatings) are formed by vapor deposition. By setting the reflectance of reflection mirror 3 at 80 to 95% and the reflectance of reflection mirror 4 at 99.5% or more, which is semi-perfect reflection, laser light amplification becomes possible. Moreover, there are also cases where laser light emitted from laser rod 2 is focused on one point and intensified with condenser lens 7 placed on emission axis of laser rod 2.    Patent Document 1: Japanese Patent Application Laid-Open No. HEI07-115237
The amount of laser light emission is determined by the product of the amount of light emission of the excitation light source including a flashlamp, energy conversion rate, and the volume of the laser rod.
Increasing the end face diameter of the laser rod, that is, making the laser rod thicker, is one method of increasing the amount of laser light emission. However, a thick laser rod is usually expensive. Moreover, the diameter of laser light of a laser radiation apparatus is determined by the diameter of the end face of the laser rod. Consequently, to condense laser light emission, it is necessary to use a lens of a larger diameter than the laser rod. If laser light from a large emitting diameter is used, the length of the diameter of the focus cannot be made smaller than a certain level.
To increase the amount of laser light emission without making the emitting diameter of the laser rod larger, it is necessary to make the length of the laser rod longer, that is, make the laser rod slimmer. However, if a laser rod is made longer, there is a problem that resistance to shock or drop is reduced.
As described above, there is a limit to increase the amount of laser light emission by increasing the volume of the laser rod.
Furthermore, in a conventional laser light emission apparatus, a flashlamp is placed in only one side of the laser rod, which then results in a problem of low energy conversion rate. For example, the ratio (conversion rate) of energy inputted to a xenon flashlamp to the energy produced as laser light, is about 1% or less.
The present invention is implemented in view of the above-described problems, and it is therefore an object of the present invention to provide a laser radiation apparatus that is compact and that enables substantial emission intensity.